Von Jest zu Vitest migrieren

Compatibility

Vitest was designed around a Jest-compatible API, so most test files move over by swapping jest.* calls for vi.* and importing from vitest. The differences below are the ones the Vitest team documents.

Before you switch

1. Decide on globals. Jest exposes describe, it and expect globally by default and Vitest does not: turn on the globals option, or import them from vitest.
2. Replace jest.fn, jest.mock and jest.spyOn with their vi counterparts, and jest.setTimeout(n) with vi.setConfig({ testTimeout: n }).
3. Import types such as Mock from vitest, since there is no jest namespace.

Pitfalls

• With globals off, Testing Library does not clean up the DOM automatically between tests.
• mockReset restores the original implementation passed to vi.fn, where Jest replaces it with an empty function.
• A module mock factory must return an object with each export spelled out, including default. In Jest, the returned value is the default export.
• Mocks in __mocks__ are not picked up unless vi.mock() is called, for example in a setup file.
• jest.requireActual becomes await vi.importActual.
• Test names are joined with > instead of a space, which changes expect.getState().currentTestName and -t patterns that span a suite and a test.
• Tests written with a done callback must become async functions.
• A beforeEach or beforeAll that returns a value is treated as a teardown function. Hooks also run as a stack by default; set sequence.hooks to list for Jest’s order.
• JEST_WORKER_ID becomes VITEST_POOL_ID, and Jest’s legacy fake timers are not supported.